Ping: backport fix for PR 48660 (assigning to BLKmode return regs)

[Richard Sandiford]

Ping for backporting this expand patch, which fixes an ice-on-valid
regression from 4.4 while compiling certain C++ packages on ARM:

   http://gcc.gnu.org/ml/gcc-patches/2011-12/msg01550.html

As I understand it, this bug is the only reason Ubuntu is keeping
a GCC 4.4 package: there's no known workaround besides changing the
source, so affected packages have to be compiled with an older compiler.
I think this is going to be one of those patches that distros who care
about ARM will end up having to backport individually if we don't do it
in the FSF version.

Richard